This R01 is submitted in response to RFA-MH-07-090 Innovative Trials for the Treatment of Anorexia Nervosa in Late Adolescence and Adulthood. With a specific focus on adult anorexia nervosa (AN), we propose to unite the expertise of a team skilled in the treatment of AN with world leaders in the development of couple-based interventions to develop an innovative intervention for couples in which one member is suffering from AN. The intervention "UCAN: Uniting Couples (in the treatment of) Anorexia Nervosa" acknowledges that AN occurs in an interpersonal context, both being affected by the person's social environment and impacting important interpersonal relationships. Moreover, the demonstrated success of family therapy for younger individuals with AN underscores the importance of leveraging family support in the treatment of AN. UCAN tailors cognitive-behavioral couple-based interventions that have been employed successfully for the treatment of depression, anxiety disorders, smoking cessation, and cancer to address the core psychopathology of AN, while also addressing the unique and challenging stresses that AN places on intimate relationships. Our initial conceptualization of the intervention focuses first on addressing AN within the context of the relationship with foci such as altering interactions around eating and weight, normalizing activity and health behaviors, body image, physical affection, and sexuality and second on addressing the broader relationship to maintain treatment gains, prevent relapse, and foster relationship satisfaction. The specific aims are: 1) to develop and standardize a manualized intervention for couples in which one member suffers from AN;2) to determine feasibility and acceptability of a beta- version of UCAN in an open trial as an augmentation to treatment as usual (TAU) and to refine UCAN based on feedback from the preliminary trial;3) to test UCAN+TAU versus TAU in a randomized controlled trial of 24 couples in which one member has AN;and 4) to adapt an observational couples assessment measure with the eventual goal of incorporating biological measures of affiliation and stress. Our primary patient outcomes will be BMI and global improvement, and our secondary patient outcomes will be depression, anxiety, and relationship adjustment and communication. Partner outcomes will also include caregiving measures. This trial will be designed explicitly to gather preliminary outcome data to inform sample size and power calculations for a subsequent larger randomized controlled trial. Findings from this investigation have the potential to result in the creation of an effective, acceptable, developmentally tailored intervention that will improve both core AN pathology as well as couple functioning. Future extensions of the intervention will include couple-based interventions for eating disorders such as bulimia nervosa and binge eating disorder. We propose to develop a couple-based intervention for adults with anorexia nervosa entitled "UCAN: Uniting Couples (in the treatment of) Anorexia Nervosa." We will create an effective, acceptable, developmentally tailored intervention that leverages the support of partners to improve both core anorexia nervosa pathology as well as couple functioning.